1. Field of the Invention
The present invention relates to a variator for a toroidal transmission, with a driving disk and with a driven disk, between which is set up a toroidal space which defines a toroidal reference circle, and with at least two rollers which are arranged in the toroidal space for torque transfer between the driving disk and the driven disk, the rollers being in each case mounted rotatably on a roller carrier, the roller carriers being in each case spatially adjustable by means of a piston/cylinder arrangement, in order to adjust the transfer ratio of the variator, and the pistons of the piston/cylinder arrangements being in each case adjustable along a stroke axis.
The present invention relates, furthermore, to a variator arrangement consisting of two or more variators of the type mentioned.
2. Description of the Related Art
In the field of transmissions, in particular of transmissions for motor vehicles, there is a trend toward continuously variable transmissions. Continuously variable transmissions, in general, make it possible to operate the internal combustion engine that is arranged in series with the transmission in motor vehicles, in a favorable rotational speed range independently of the respective vehicle speed. The efficiency of the drivetrain formed by the internal combustion engine and the continuously variable transmission is thereby improved. Furthermore, continuously variable transmissions afford a particularly high degree of driving comfort.
Among continuously variable transmissions, toroidal transmissions, as they are known, have particular importance, specifically especially because of their higher torque capacity, as compared with continuously variable wrap-around transmissions (CVTs).
Among toroidal transmissions, the Torotrak™ system is of particular significance (cf. www.torotrak.com). This transmission manages without an input-side starting clutch or a hydrodynamic torque converter. It is a full-toroidal transmission which is generally constructed in the manner of a countershaft transmission. The variator ensures a continuous adjustment of the ratio. A planet wheel set serves as a summing transmission.
The core of the toroidal transmission is the variator of the type initially mentioned or an arrangement consisting of a plurality of such variators.
In transmission designs put forward at the present time, the piston/cylinder arrangements for the spatial adjustment of the roller carriers are arranged tangentially with respect to the toroidal reference circle and spatially well outside the maximum diameter of the toroidal disks (driving and driven disk). As a result of this arrangement, the cylinders project well beyond the actual contour of the variator, the consequence of this being that the toroidal transmission, overall, has a large build in the radial direction (unfavorable package). On account of this, the designs of toroidal transmissions known at the present time can be fitted only with difficulty to the tunnel contour of vehicles having standard longitudinal drive trains.